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Huang W.,Key Laboratory of Biological Resources Protection and Utilization in Tarim Basin | Huang W.,Tarim University | Li Z.,Key Laboratory of Biological Resources Protection and Utilization in Tarim Basin | Li Z.,Tarim University | And 4 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2010

Populus euphratica Oliv., a member in the family Salicaceae, is mainly distributed in central Asia, west Asia and the Mediterranean region, especially in Xinjiang of China and Kazakhstan where it occupies the widest distribution aiea. P. euphratica poseeses many excellent characteristics such as cold tolerance, high temperature resistant, anti-drought, anti-sand, salt and alkali resistant etc. It plays an active role in climatic regulation, desert extension control, bank protection, channels stabilization and oasis conservation. It has not only protected desert fragile ecological system but also been an irreplaceable natural barrier in the ecological security maintenance and sustainable socio-economic development. During the growth and development of P. euphratica, the leaf morphology changed accordingly. The linear, lanceolate, ovate, or broadly ovate leaves come out in turn. In one plant with four types of leaf shapes at the same time, the heteromorphic leaf distribution in the canopy from top to bottom is broadly ovate, ovate, lanceolate, or linear, respectively. In one growth season, the leaves with small length/wide ratio appears earlier in the plant, which means that broadly ovate leaves at the top of canopy expansion first, and then the ovate leaves, lanceolate leaves, linear leaves at lower layer expansion one by one. Through analysis of five indices of structural traits, e. g. thickness (TH), area (AR), specific leaf area (SLA), dry weight (DW) and dry matter content (DMC) with four leaf shapes (broadly ovate, ovate, lanceolate and linear, respectively) of Populus euphratica, the relationship between structural traits of Populus euphratica heteromorphic leaves and length/width (L/W) and the correlations among five indices would be investigated. The results showed that, the L/W of leaves was significantly negatively correlated with their TH, DMC, AR, DW (P < 0.05), but positively correlated with their SLA. It indicated that the growth and development process of the P. euphratica individual, is also a process of increasing leaf area and leaf thickness, development of xerophytic structure, and increase of photosynthesis rate along with the leaves shape changing. It indicated that it the emerge of different leaf types results in bigger photosynthetic area, higher net photosynthetic rate, more accumulation of photosynthate and excellent guard structure gradually. Thus P. euphratica plant dramatically improve its photosynthetic area by increasing the leaf area and the leaf thickness and forming the developed stockade tissue to meet the demands of plant nutrient. On the other hand, P. euphratica plant improves the diffusion distance or the resistance from the leaf internal to the surface by increasing leaf thickness, cutin layer thickness and cell number of mucous etc., and improved the leaf water retaining capacity. The water dissipation was reduced to be a certain degree. It is also illustrated that the leaf shape changing in the growth process of P. euphratica is an adaptability performance of its survival and growth. Correlations among structural characteristics indices showed that, the SLA of leaves was significantly negatively correlated with DMC and DW (P < 0.05), and more significantly negatively correlated with their TH (P < 0.01), the TH of leaves was more significantly positively correlated with DMC (P < 0.01), and the DW of leaves was more significantly positively correlated with SLA (P <0.01). There were no significant correlations among other indices.

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